The Great Depression
What is the biggest lesson from the Great Depression? In my view, it is that monetary policy and the financial sector play a crucial role in economic development. Let me put it more precisely: good monetary policy is unlikely to accelerate the speed of economic growth - after all we have more income year after year because mankind comes up with new ideas, with new products, with more efficient ways of producing output. However, bad monetary policy can easily derail economic development. It is true for rich and poor countries alike. Why are financial markets and the banking sector so important? Banks fulfill a very important role in the economy by matching borrowers and lenders. When we deposit $100 in a bank, the bank keeps, at most, two to three dollars in its vaults (in fact the money is often in the central bank), the remaining $98 or so is lent to a borrower. Most businesses require loans for their normal operations. When the banking sector does not work properly, businesses cannot get loans and they have to curtail their production and lay off workers. As they curtail production, they demand fewer products from their suppliers and therefore their suppliers have to reduce their output and fire workers. If manufacturers cannot sell their goods because the firm downstream does not need as many products as before, they cannot generate enough revenue to repay their earlier loans. Businesses go bankrupt and banks experience further problems as their balance sheet deteriorates due to non-performing loans. At this point, banks want to lend even less because of the uncertainty generated from bankruptcies. As they lend less, the vicious circle continues - with producers cutting production and firing workers. On the top of this, depositors start worrying about their deposits because the non-performing loans have made some banks go belly up - your bank has lent out your money to borrowers who cannot return it. Depositors start withdrawing their cash and banks have even fewer possibilities for lending as they have to hoard cash in case there is a run on the bank. If the financial sector does not work, the real economy can go into a deadly spiral and shrink by 30 per cent as during the Great Depression. And one thought like Ilian that this would be obvious to all the policy makers. However all the lessons from the Great Depression seem to have been lost within three-quarters of a century. It seems, to paraphrase Marc Bard, that politics [especially of the petty and partisan variety] eats policy for lunch seven days a week.
Ekagra Agarwal
US vs UK- Media
News media businesses can no longer rely solely on making money from traditional advertising and must embrace the multiple commercial opportunities from online, according to magazine publisher and broadcaster Andrew Neil. The Press Holdings chairman, BBC presenter and former Sunday Times editor said the changes sweeping the media industry were "transformative and revolutionary" and that traditional ways of making money had all but eroded as increased competition and the explosion of online media erodes the exclusivity of advertising deals. Speaking at today's SIIA Global Information Industry Summit in London, Neil said that the internet was not a threat to the traditional printed media companies, but an "essential" opportunity to diversify and ultimately save them. "Sensible newspaper and magazine publishers do not see online as a threat or something they have to do because 'it is the future, so let's do it and grit our teeth'," he said. "Offline publications are still necessary for brand building and because people still like to hold a newspaper or particularly a magazine. But the revenues for that are in decline as search engines make classified ads increasingly irrelevant." Neil pointed out that his magazine websites (- he is also chairman of ITP Publishing, the Gulf's largest magazine publishers) were visited mainly by people who also read the print version and visit the site "for the additional material that is only online". He said The Spectator, owned by Press Holdings, had achieved great success with its Coffee House network of blogs, which has 200,000 unique users a month and will contribute "20 per cent of the bottom line" this year in terms of revenue. He also pointed out that the one of the biggest spikes in traffic for Telegraph.co.uk was around 10am every day, when the print readers had finished their Daily Telegraph and wanted to know what else its journalists were doing. "You now need to use online to do a whole host of things that you just could not before," he added. "It ceases to be an either-or situation." Neil admitted the going was tough for the media in a multi-platform world with complex revenue streams but it was, for him at least, "a lot more fun". He contrasted the UK market with the US, in which newspapers are run by big city monopolies that are unused to competition and "run for the journalists and not for the readers". In the UK many mainstream publishers grasped the need to diversify early on: "Most trends like this begin in the US but in this trend the British media are particularly much ahead of them," he said. "British newspapers have always been used to competition: it's the most competitive newspaper market in the world bar none."
Spaced out
All astronauts look forward to living in the lonely and unpredictable environment of space. In low earth orbit, for instance, you get to see 16 sunrises and 16 sunsets! For the day fades into night every 45 minutes as the spacecraft rotates slowly to keep its solar panels facing the sun. Viewers in Delhi shared a bit of this excitement with Sunita Williams aboard the international Space Station, when she telechatted with them earlier this month. Astronauts spend long periods in weightlessness of 'zero gravity'. It may be fun for us sitting in our gravity cocooned rooms and watching them on TV, as they float around. But inside their bodies things are happening that aren't any fun at all. Scientists study the effects of outer space on the human body to see how it behaves in zero gravity and then re-adapts to earth`s gravity at the end of the spaceflight. In space the number of red blood cells, bone and muscle tissues are all altered and the metabolic process upset. On Earth, gravity pulls blood to lower body, away from the head. Nerves called the baroreceptors detect this and redirect blood flow, ensuring that the brain gets enough oxygen and sugar. In space baroreceptors don't sense any pressure difference and the astronaut flies with an atypical redistribution of blood. On earth we build bones by running or jumping. But without gravity, the bones begin to lose calcium, which is absorbed in the body. (Bedridden and paraplegics suffer the same problem, losing 30% of their lower body bone mass within months). The minerals lost from the leg and hipbones aren't excreted and they migrate to the head, making the skull dense. This is the body's way of making better use of its resources: legs are useless in space, so the body moves to protect the brain!. Unlike on earth there is no muscle tension in space. Muscles are relaxed, stretched and actually grow by five to seven inches in a space flight. Surprisingly one gets taller while one sleeps, too, because of relaxed muscles - sometimes enough to readjust one's car's rear-view mirror in the morning. To offset this, the astronauts aboard the ISS exercise on a treadmill every day. So every space payload has a large component of medical experiments to help scientists figure out what we gain-or lose-up there.
History of Relativity
In December of 1923 a piece of doggerel appeared in Punch, poking fun at Albert Einstein's newly famous theory of relativity. The piece was unsigned, but years later A.H. Reginald Buller stepped forward to claim authorship. He was a fellow of the Royal Society of Canada and came from a different field of science: he was editor of the seven-volume Researches in Fungi. In the early years, experimental support for relativity theory was meager: full vindication of Albert Einstein's ideas was still to come. Relativity theory had drawn startling conclusions concerning the four most basic physical quantities-length, time, mass, and energy. In the course of the century, these results would receive direct and very striking experimental confirmation. The relativistic effects also became the basis for new technologies, such as Global Positioning Systems (GPS), whose continued functioning would verify these effects every day and every passing hour. The disruption of time was the most fundamental conclusion. Both in Einstein's technical paper of 1905 and in Relativity Clear and Simple, the relativity of simultaneity formed the basis for all subsequent discussion. In particular, Einstein showed that moving clocks as compared with stationary clocks would run slow as a result of their motion. As Einstein was philosophically committed to the idea that time was nothing more nor less than what you could measure with standardized clocks, he necessarily concluded that time itself passed more slowly in a moving frame of reference and the faster the motion of the reference frame, the slower the passage of time. This was called time dilation: time slows down, stretches out, in a moving reference frame. This was the most revolutionary conclusion of relativity theory. It was also, for a period of more than thirty years, completely unsupported by any direct experimental evidence. Critics of relativity theory, of course, jumped on Einstein: Wasn't it ridiculous to make the claim on the basis of no direct evidence whatsoever-that time itself could slow down? And wouldn't various paradoxes and absurdities result from this kind of elasticity of time? Would an astronaut who travelled in a rocket ship at high velocity age less than his twin who stayed at home? If time could slow down as a result of motion at high speed, would time reverse if one went fast enough? Discussion of time dilation left the realm of the fanciful when it became possible to verify this effect in a direct manner. This first occurred in 1941, when time dilation was detected in experiments on cosmic rays. The earth is continually bombarded by atomic particles from outer space. These swiftly moving particles are the "primary" cosmic rays. When the particles reach the top of the atmosphere, they collide with atomic nuclei. Subatomic debris is produced, constituting the "secondary" cosmic rays, which then travel downward toward the surface of the earth. In particular, particles called muons are produced in the upper atmosphere and move downward toward the surface. Muons are highly unstable particles, having an average lifetime of about a millionth of a second. Given the short lifetimes of the muons and the long distances they have to travel to get down to the surface of the earth, one can calculate that, given the velocities at which they travel, very few of them should actually make it down to sea level. However, large numbers can be detected- many more than expected. It appears that, somehow, the moving muons have longer lifetimes than expected, so that they can travel longer distances than expected. This is exactly what would be expected on the basis of time dilation. The muons are traveling at velocities comparable to the velocity of light, and their internal "clocks" should slow down as a result-in accordance with Einstein's prediction-so that many more are able to reach the surface of the earth than would be otherwise expected. Precise experiments on muons gave results exactly in accord with Einstein's equation for time dilation, verifying the effect quite convincingly. Experimental technologies used in particle physics have come to rely on time dilation for their successful day-to-day operation. For those who are not particle physicists, verification of time dilation has become possible with the development of a device known as an atomic clock, which can measure time intervals to a precision of one part in a trillion. Consider flying in an airplane at five hundred miles per hour. This produces minimal time dilation, and air travelers have not noticed their watches running slow as a result of this effect. Calculations on the basis of Einstein's equation for the time dilation, however, show that the expected effort is a slowing down by about one part in a trillion, which should be measurable by an atomic clock. In 1971, a team of scientists who were experts in the use of atomic clocks set out to detect and measure time dilation and other relativistic effects. The research team was able to devise a cheap and effective plan, which received some support from the Office of Naval Research. We are told that the researchers purchased three around-the-world tickets on regularly scheduled commercial airliners-two tickets for the accompanying scientists and one for an array of four atomic clocks. The clock array had its own seat; it sat, belted in for safety, between its two caretakers. Before leaving on the trip, the clocks were synchronized with a master clock at the U.S. Naval Observatory. The four clocks then went around the world, following which they were compared again with their counterpart, which had stayed behind at the Naval Observatory. After correcting for the rotation of the earth and the variation of the force of gravity with altitude, it was found that the clocks that had been in motion in their journey around the earth had in fact slowed as compared with the clock at the Naval Observatory, and by exactly the amount predicted by the theory of relativity. The result was further confirmed in a second around-the-world flight in the opposite direction.
Feynam Physics-Lenses
Before we get too excited about how marvelous lenses are, we must hasten to add that there are also serious limitations, because of the fact that we have limited ourselves, strictly speaking, to paraxial rays, the rays near the axis. A real lens having a finite size will, in general, exhibit aberrations. For example, a ray that is on the axis, of course, goes through the focus; a ray that is very close to the axis will still come to the focus very well. But as we go farther out, the ray begins to deviate from the focus, perhaps by falling short, and a ray striking near the top edge comes down and misses the focus by quite a wide margin. So, instead of getting a point image, we get a smear. This effect is called spherical aberration, because it is a property of the spherical surfaces we use in place of the right shape. This could be remedied, for any specific object distance, by re-forming the shape of the lens surface, or perhaps by using several lenses arranged so that the aberrations of the individual lenses tend to cancel each other. Lenses have another fault : light of different colors has different speeds, or different indices of refraction, in the glass, and therefore the focal length of a given lens is different for different colors. So if we image a white spot, the image will have colors, because when we focus for the red, the blue is out of focus, or vice versa. This property is called chromatic aberration. There are still other faults. If the object is off the axis, then the focus really isn't perfect any more, when it gets far enough off the axis. The easiest way to verify this is to focus a lens and then tilt it so that the rays are coming in a large angle from the axis. Then the image that is formed will usually be quite crude, and there may be no place where it focuses well. There are thus several kinds of errors in lenses that the optical designer tries to remedy by using many lenses to compensate each other's errors. How careful do we have to be to eliminate aberrations? Is it possible to make an absolutely perfect optical system? Suppose we had built an optical system that is supposed to bring light exactly to a point. Now, arguing from the point of view of least time can we find a condition on how perfect the system has to be? The system will have some kind of an entrance opening for the light. If we take the farthest ray from the axis that can come to the focus (if the system is perfect, of course), the times for all rays are exactly equal. But nothing is perfect, so the question is, how wrong can the time be for this ray and not be worth correcting any further? That depends on how perfect we want to make the image. But suppose we want to make the image as perfect as it possibly can be made. Then, of course, our impression is that we have to arrange that every ray takes as nearly the same time as possible. But it turns out that this is not true, that beyond a certain point we are trying to do something that is too fine, because the theory of geometrical optics does not work! Remember that the principle of least time is not an accurate formulation, unlike the principle of conservation of energy or the principle of conservation of momentum. The principle of least time is only an approximation, and it is interesting to know how much error can be allowed and still not make any apparent difference. The answer is that if we have arranged that between the maximal ray--the worst ray, the ray that is farthest out--and the central ray, the difference in time is less than about the period that corresponds to one oscillation of the light, then there is no use improving it any further. Light is an oscillatory thing with a definite frequency that is related to the wavelength, and if we have arranged that the time difference for different rays is less than about a period, there is no use going any further.